Today's enterprise data centers are designed with a silo-oriented architecture in mind where each application has its own dedicated servers, storage and network infrastructure. A software stack tailored for the application controls these resources as a whole. Due to the stringent requirements placed on the enterprise applications and the time-varying demands that they experience, each application silo is vastly over-provisioned to meet the application service goals. As a result, data centers are often under-utilized, while some nodes may sometimes become heavily-loaded, resulting in service-level violations due to poor application performance.
One approach to increase resource utilization is to consolidate applications in a shared infrastructure using virtualization. Meeting application-level quality of service (QoS) goals becomes a challenge in a consolidated environment as application resource needs differ. Furthermore, for multi-tier applications, the amount of resources needed to achieve QoS goals might be different at each tier and may also depend on availability of resources in other tiers.